 IXPE satellite, on the top are its three identical X-ray optics elements, the sensors are on the bottom. | |
| Names | Explorer 97 IXPE SMEX-14 |
|---|---|
| Mission type | X-ray polarimetry |
| Operator | NASA,ASI |
| COSPAR ID | 2021-121A |
| SATCATno. | 49954 |
| Website | ixpe asi.it/ixpe |
| Mission duration | 5 years (planned) 3 years, 11 months and 10 days (in progress) |
| Spacecraft properties | |
| Spacecraft | Explorer XCVII |
| Spacecraft type | Imaging X-ray Polarimetry Explorer |
| Bus | BCP-100 |
| Manufacturer | Ball Aerospace & Technologies OHB Italia |
| Launch mass | 330 kg (730 lb)[1] |
| Payload mass | 170 kg (370 lb) |
| Dimensions | 1.1 m (3 ft 7 in) in diameter and 5.2 m (17 ft) tall, fully extended Solar array: 2.7 m (8 ft 10 in) fully deployed |
| Start of mission | |
| Launch date | 9 December 2021, 06:00 UTC[3] |
| Rocket | Falcon 9B1061-5 |
| Launch site | Kennedy Space Center,LC-39A |
| Contractor | SpaceX |
| Entered service | 10 January 2022[2] |
| Orbital parameters | |
| Reference system | Geocentric orbit |
| Regime | Low Earth orbit |
| Perigee altitude | 540 km (340 mi) |
| Apogee altitude | 540 km (340 mi) |
| Inclination | 0.20° |
| Period | 90.00 minutes |
| Main telescope | |
| Type | Three-mirror |
| Focal length | 4 m[4] |
| Wavelengths | X-ray |
| Transponders | |
| Band | S-band[5] |
_logo.png){kind=logo} IXPE mission logo | |
Imaging X-ray Polarimetry Explorer, commonly known asIXPE orSMEX-14, is aspace observatory with three identical telescopes designed to measure thepolarization ofcosmic X-rays of black holes, neutron stars, and pulsars.[6] The observatory, which was launched on 9 December 2021, is an international collaboration betweenNASA and theItalian Space Agency (ASI). It is part of NASA's Explorers program, which designs low-cost spacecraft to study heliophysics and astrophysics.
The mission will study exotic astronomical objects and permit mapping of the magnetic fields ofblack holes,neutron stars,pulsars,supernova remnants,magnetars,quasars, andactive galactic nuclei. The high-energyX-ray radiation from these objects' surrounding environment can be polarized – oscillating in a particular direction. Studying thepolarization of X-rays reveals the physics of these objects and can provide insights into the high-temperature environments where they are created.[7]
The IXPE mission was announced on 3 January 2017[6] and was launched on 9 December 2021.[3] The international collaboration was signed in June 2017,[1] when theItalian Space Agency (ASI) committed to provide the X-raypolarization detectors.[7] The estimated cost of the mission and its two-year operation is US$188 million (the launch cost is US$50.3 million).[8][7] The goal of the IXPE mission is to expand understanding of high-energyastrophysical processes and sources, in support of NASA's first science objective in astrophysics: "Discover how the universe works".[1] By obtaining X-ray polarimetry and polarimetric imaging of cosmic sources, IXPE addresses two specific science objectives: to determine the radiation processes and detailed properties of specific cosmic X-ray sources or categories of sources; and to exploregeneral relativistic andquantum effects in extreme environments.[1][6]
During IXPE's two-year mission, it will study targets such asactive galactic nuclei,quasars,pulsars,pulsar wind nebulae,magnetars,accreting X-ray binaries,supernova remnants, and theGalactic Center.[4]
The spacecraft was built byBall Aerospace & Technologies.[1] The principal investigator isMartin C. Weisskopf of NASAMarshall Space Flight Center; he is the chief scientist forX-ray astronomy at NASA's Marshall Space Flight Center and project scientist for theChandra X-ray Observatory spacecraft.[7] NASA's Marshall Space Flight Center also designed, manufactured, and tested the X-ray mirrors for the telescope.[9]
Other partners include theMcGill University,Massachusetts Institute of Technology (MIT),Roma Tre University,Stanford University,[5]OHB Italia[10] and theUniversity of Colorado Boulder.[11]
The technical and science objectives include:[3]
The space observatory features three identical telescopes designed to measure thepolarization ofcosmic X-rays.[6] The polarization-sensitive detector was invented and developed by Italian scientists of theIstituto Nazionale di AstroFisica (INAF) and theIstituto Nazionale di Fisica Nucleare (INFN) and was refined over several years.[4][12][13]
| Telescope (×3) | Basic parameters |
|---|---|
| Wavelength | X-ray |
| Energy range | 2–8keV |
| Field of view (FoV) | >11′ |
| Angular resolution | ≤30″ |
IXPE's payload is a set of three identical imaging X-ray polarimetry systems mounted on a common optical bench and co-aligned with the pointing axis of the spacecraft.[1] Each system operates independently for redundancy and comprises a mirror module assembly that focuses X-rays onto a polarization-sensitive imagingdetector developed in Italy.[1] The 4 m (13 ft) focal length is achieved using a deployable boom.
The Gas Pixel Detectors (GPD),[14] a type ofMicropattern gaseous detector, rely on theanisotropy of the emission direction ofphotoelectrons produced by polarized photons to gauge with high sensitivity the polarization state of X-rays interacting in a gaseous medium.[4] Position-dependent and energy-dependent polarization maps of suchsynchrotron-emitting sources will reveal the magnetic-field structure of the X-ray emitting regions. X-ray polarimetric imaging better indicates the magnetic structure in regions of strong electron acceleration. The system is capable to resolvepoint sources from surroundingnebular emission or from adjacent point sources.[4]
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IXPE was launched on 9 December 2021 on a SpaceX Falcon 9 (B1061.5) fromLC-39A at NASA'sKennedy Space Center in Florida. The relatively small size and mass of the observatory falls well short of the normal capacity of SpaceX's Falcon 9launch vehicle. However, Falcon 9 had to work to get IXPE into the correct orbit because IXPE is designed to operate in an almost exactly equatorial orbit with a 0°inclination. Launching fromCape Canaveral, which is located 28.5° above theequator, it was physically impossible to launch directly into a 0.2° equatorial orbit. Instead, the rocket needed to launch due east into a parking orbit and then perform aplane, or inclination, change once in space, as the spacecraft crossed the equator. For Falcon 9, this meant that even the tiny 330 kg (730 lb) IXPE likely still represented about 20–30% of its maximum theoretical performance (1,500–2,000 kg (3,300–4,400 lb)) for such a mission profile, while the same launch vehicle is otherwise able to launch about 15,000 kg (33,000 lb) to the same 540 km (340 mi) orbit IXPE was targeting when no plane change is needed, while recovering the first stage booster.[15]
IXPE is the first satellite dedicated to measuring the polarization of X-rays from a variety of cosmic sources, such asblack holes andneutron stars. The orbit hugging the equator will minimize the X-ray instrument's exposure to radiation in theSouth Atlantic Anomaly, the region where the innerVan Allen radiation belt comes closest to Earth's surface.
IXPE is built to last for two years.[8] After that it may be retired and deorbited or given an extended mission.
After launch and deployment of the IXPE spacecraft, NASA pointed the spacecraft at 1ES 1959+650, a black hole, and SMC X-1, a pulsar, for calibration. After that the spacecraft observed its first science target,Cassiopeia A. Afirst-light image of Cassiopeia A was released on 11 January 2022.[16] 30 targets are planned to be observed during IXPE's first year.[16]
IXPE communicates with Earth via aground station in Malindi, Kenya. The ground station is owned and operated by the Italian Space Agency.[16]
At present mission operations for IXPE are controlled by theLaboratory for Atmospheric and Space Physics (LASP).[17]
In May 2022 the first study of IXPE hinted the possibility of vacuum birefringence on4U 0142+61[18][19] and in August another study looked atCentaurus A measuring low polarization degree, suggesting that the X-ray emission is coming from a scattering process rather than arising directly from the accelerated particles of the jet.[20][21] In October 2022 it observed thegamma ray burstGRB 221009A, also known as the "Brightest of all time" (BOAT).[22][23]
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